This invention relates to a novel anti-malignant tumor agent comprising a combination of 5-fluorocytosine and cytosinedeaminase. It is understood that the term "tumor" as employed herein means tumors sensitive to 5-fluorouracil.
Nowadays, a considerably large number of compounds are used as antitumor agents for clinical treatment. They include, for example, alkylating agents, nucleic acid-type antimetabolites, antitumor antibiotics, and hormonal agents, and the like. In many cases, however, these antitumor agents are used against leukemia and malignant lymphoma and the like, and few are effective against solid tumors such as stomach cancer, and the like. Although 5-fluorouracil is known to be effective against solid tumors, it has the drawback of intense toxicity in oral and intravenous administrations.
There was suggested tetrahydrofuryl 5-fluorouracil as an orally administrable agent free from this drawback. This compound in fact has low toxicity, however, its antitumor activity is also low, accordingly.
In an attempt to remove these drawbacks of known antitumor agents, the present inventors have made an effort to develop new therapeutic agents against malignant tumors which have lower toxicity and higher efficacy. These investigations have led to the unexpected discovery that administration, preferably topical administration, of cytosinedeaminase in the presence of 5-fluorocytosine causes necrosis of tumor tissues alone without giving any adverse effect on the entire human body.